1. Field of the Invention
The present invention relates to fuel delivery and vapor recovery systems, and more specifically to an apparatus and method for the vapor recovery of vapors associated with propane fuel delivery systems.
2. Description of Related Art
Gasoline dispensing facilities, such as service stations, often suffer from a loss of fuel to the atmosphere due to inadequate vapor collection during fuel dispensing activities. Lost vapor is an air pollution problem which is monitored and regulated both by the federal and state governments. Attempts to minimize losses to the atmosphere have been affected by various vapor recovery methods. One such method is “Stage-II vapor recovery” where vapors are returned from the refueled vehicle tank to the underground storage tank.
When working properly, Stage-II vapor recovery results in equal exchanges of air of vapor and liquid between the main fuel storage tanks and the consumer's gas tank. Ideally, returned vapor replaces an equal amount of liquid in the main fuel storage tank during refueling transactions. A variety of vapor recovery nozzles exist today. Typically, a vapor recovery nozzle works with a vapor recovery fuel dispensing line to return vapors from the vehicle tank being fueled while simultaneously delivering fuel from the main storage tank to the vehicle fuel tank. There are at least two types of vapor recovery systems in use today. A vapor assist system typically utilizes vacuum to return the vapors from the vehicle tank being fueled to the main storage tank. A balance system typically utilizes the ingoing fuel to displace the air/vapor in the tank being fueled and return the air/vapor to the main storage tank.
Propane fueling also occurs at many service stations. The propane fueling regime typically results in the venting of significant quantities of propane vapor into the atmosphere either during fueling or subsequent to the filling of propane cylinders during the venting of fill lines. The venting of propane is beginning to be viewed more harshly with regard to environmental impact. Some jurisdictions are considering increased scrutiny of the propane fueling process.
The release of propane into the atmosphere is generally misunderstood. Propane is considered a clean gas, and generally viewed as environmentally friendly. What most people do not understand is that when propane is released into the atmosphere as an unburned gas that it is a very concentrated pollutant. Propane is a volatile organic compound (VOC), and VOCs are one of the key ingredients in smog. VOCs also play a role in the formation of ozone, which can harm plants and people when present at low altitude and in high concentrations. It has been estimated that 336 million pounds of unburned propane escape into the atmosphere every year.
What is called for is an efficient apparatus and method to recover the vapors that have been heretofore discharged into the environment during propane fueling.